Last visit was: 23 May 2024, 05:16 It is currently 23 May 2024, 05:16
Toolkit
GMAT Club Daily Prep
Thank you for using the timer - this advanced tool can estimate your performance and suggest more practice questions. We have subscribed you to Daily Prep Questions via email.

Customized
for You

we will pick new questions that match your level based on your Timer History

Track

every week, we’ll send you an estimated GMAT score based on your performance

Practice
Pays

we will pick new questions that match your level based on your Timer History
Not interested in getting valuable practice questions and articles delivered to your email? No problem, unsubscribe here.

# John traveled the entire 50 km trip. If he travelled the first 20 km o

SORT BY:
Tags:
Show Tags
Hide Tags
Math Revolution GMAT Instructor
Joined: 16 Aug 2015
Posts: 10152
Own Kudos [?]: 16719 [1]
Given Kudos: 4
GMAT 1: 760 Q51 V42
GPA: 3.82
CEO
Joined: 26 Feb 2016
Posts: 2873
Own Kudos [?]: 5234 [0]
Given Kudos: 47
Location: India
GPA: 3.12
GMAT Club Legend
Joined: 12 Sep 2015
Posts: 6817
Own Kudos [?]: 30306 [1]
Given Kudos: 799
Director
Joined: 21 May 2013
Posts: 540
Own Kudos [?]: 228 [0]
Given Kudos: 608
Re: John traveled the entire 50 km trip. If he travelled the first 20 km o [#permalink]
MathRevolution wrote:
[GMAT math practice question]

John traveled the entire 50 km trip. If he traveled the first 20 km of the trip at a constant rate 40 km per hour and the remaining trip at a constant rate 20 km per hour, what is his average speed, in km per hour?

A. 20 km/h
B. 23 km/h
C. 25 km/h
D. 26 km/h
E. 27 km/h

Average Speed= Total distance traveled/Total time taken
=50/(20/40+30/20)
=50/2=25
Math Revolution GMAT Instructor
Joined: 16 Aug 2015
Posts: 10152
Own Kudos [?]: 16719 [0]
Given Kudos: 4
GMAT 1: 760 Q51 V42
GPA: 3.82
Re: John traveled the entire 50 km trip. If he travelled the first 20 km o [#permalink]
=>
Ave Speed = ( Total Distance ) / ( Total Time )
The total distance = $$50 km$$.
Total time is $$\frac{20}{40} + \frac{30}{20} = 0.5 + 1.5 = 2$$
The average speed is $$\frac{50}{2} = 25.$$

Intern
Joined: 15 Oct 2016
Posts: 20
Own Kudos [?]: 29 [0]
Given Kudos: 9
Re: John traveled the entire 50 km trip. If he travelled the first 20 km o [#permalink]
MathRevolution wrote:
[GMAT math practice question]

John traveled the entire 50 km trip. If he traveled the first 20 km of the trip at a constant rate 40 km per hour and the remaining trip at a constant rate 20 km per hour, what is his average speed, in km per hour?

A. 20 km/h
B. 23 km/h
C. 25 km/h
D. 26 km/h
E. 27 km/h

Average speed = total distance / total time = 50 / (20/40 + 30/20) = 50 / (1/2 + 3/2) = 25
Board of Directors
Joined: 11 Jun 2011
Status:QA & VA Forum Moderator
Posts: 6067
Own Kudos [?]: 4706 [0]
Given Kudos: 463
Location: India
GPA: 3.5
Re: John traveled the entire 50 km trip. If he travelled the first 20 km o [#permalink]
MathRevolution wrote:
[GMAT math practice question]

John traveled the entire 50 km trip. If he traveled the first 20 km of the trip at a constant rate 40 km per hour and the remaining trip at a constant rate 20 km per hour, what is his average speed, in km per hour?

A. 20 km/h
B. 23 km/h
C. 25 km/h
D. 26 km/h
E. 27 km/h

Time for travelling first 20 Kms = 0.50 Hr
Time for travelling first 30 Kms = 1.50 Hr

Total time taken = 2.00 Hrs

So, Average speed in kmph is $$\frac{50}{2} = 25kmph$$, Answer must be (C)
Target Test Prep Representative
Joined: 14 Oct 2015
Status:Founder & CEO
Affiliations: Target Test Prep
Posts: 18893
Own Kudos [?]: 22304 [0]
Given Kudos: 285
Location: United States (CA)
Re: John traveled the entire 50 km trip. If he travelled the first 20 km o [#permalink]
MathRevolution wrote:
[GMAT math practice question]

John traveled the entire 50 km trip. If he traveled the first 20 km of the trip at a constant rate 40 km per hour and the remaining trip at a constant rate 20 km per hour, what is his average speed, in km per hour?

A. 20 km/h
B. 23 km/h
C. 25 km/h
D. 26 km/h
E. 27 km/h

We can use the equation: average = total distance/total time

50/(20/40+ 30/20)

50/(1/2 + 3/2)

50/(4/2) = 50/2 = 25

Senior Manager
Joined: 15 Feb 2018
Posts: 424
Own Kudos [?]: 385 [0]
Given Kudos: 2380
Re: John traveled the entire 50 km trip. If he travelled the first 20 km o [#permalink]
Can harmonic mean only be used when the distance travelled is the same?
Using harmonic mean here got 26.666km/h
Non-Human User
Joined: 09 Sep 2013
Posts: 33153
Own Kudos [?]: 829 [0]
Given Kudos: 0
Re: John traveled the entire 50 km trip. If he travelled the first 20 km o [#permalink]
Hello from the GMAT Club BumpBot!

Thanks to another GMAT Club member, I have just discovered this valuable topic, yet it had no discussion for over a year. I am now bumping it up - doing my job. I think you may find it valuable (esp those replies with Kudos).

Want to see all other topics I dig out? Follow me (click follow button on profile). You will receive a summary of all topics I bump in your profile area as well as via email.
Re: John traveled the entire 50 km trip. If he travelled the first 20 km o [#permalink]
Moderator:
Math Expert
93417 posts